Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H, W = map(int, input().split())
G = [input() for _ in range(H)]
num = 0
for i in range(H):
    for j in range(W):
        if G[i][j] == ".":
            num += 1
q = deque([(0, 0)])
done = [[-1]*W for _ in range(H)]
done[0][0] = 1
while q:
    w, h = q.popleft()
    for dw, dh in [[0, 1], [0, -1], [1, 0], [-1, 0]]:
        nw, nh = w+dw, h+dh
        if not (0 <= nw < W and 0 <= nh < H and G[nh][nw] == "." and done[nh][nw] == -1): continue
        done[nh][nw] = done[h][w]+1
        q.append((nw, nh))
if done[H-1][W-1] != -1:
    print(num-done[H-1][W-1])
else:
    print(-1)